Apentix/AP Biology/Unit 1: Chemistry of Life/Question
AP Biologyeasymcq1 pt

Many signaling proteins are switched on or off when a kinase attaches a phosphate group to one of their amino acids. Why does adding this one group so often change the protein's behavior?

A.The phosphate carries negative charges that reshape the local structure and alter binding sites
B.The phosphate donates electrons that weld neighboring amino acids together permanently
C.The phosphate makes the protein lipid-soluble so it leaves the cell
D.The phosphate replaces the protein's peptide bonds with ester bonds along the backbone

Explanation

Core Concept

A covalently attached phosphate group carries one or two full negative charges at cellular pH, and that sudden electrostatic change can pull the chain into a new conformation or create and destroy docking surfaces for other molecules. Cells use this reversible switch to regulate enzymes and signaling pathways rapidly without synthesizing new protein. Electron donation, lipid solubility, and backbone rewriting are not part of phosphorylation chemistry.

Correct Answer

AThe phosphate carries negative charges that reshape the local structure and alter binding sites

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